1 /* -*- mode: c; c-file-style: "k&r" -*-
2
3 strnatcmp.c -- Perform 'natural order' comparisons of strings in C.
4 Copyright (C) 2000, 2004 by Martin Pool <mbp sourcefrog net>
5
6 This software is provided 'as-is', without any express or implied
7 warranty. In no event will the authors be held liable for any damages
8 arising from the use of this software.
9
10 Permission is granted to anyone to use this software for any purpose,
11 including commercial applications, and to alter it and redistribute it
12 freely, subject to the following restrictions:
13
14 1. The origin of this software must not be misrepresented; you must not
15 claim that you wrote the original software. If you use this software
16 in a product, an acknowledgment in the product documentation would be
17 appreciated but is not required.
18 2. Altered source versions must be plainly marked as such, and must not be
19 misrepresented as being the original software.
20 3. This notice may not be removed or altered from any source distribution.
21 */
22
23
24 /* partial change history:
25 *
26 * 2004-10-10 mbp: Lift out character type dependencies into macros.
27 *
28 * Eric Sosman pointed out that ctype functions take a parameter whose
29 * value must be that of an unsigned int, even on platforms that have
30 * negative chars in their default char type.
31 */
32
33 #include <ctype.h>
34 #include <string.h>
35 #include <assert.h>
36 #include <stdio.h>
37
38 #include "strnatcmp.h"
39
40
41 /* These are defined as macros to make it easier to adapt this code to
42 * different characters types or comparison functions. */
43 static __inline int
nat_isdigit(nat_char a)44 nat_isdigit(nat_char a)
45 {
46 return isdigit((unsigned char) a);
47 }
48
49
50 static __inline int
nat_isspace(nat_char a)51 nat_isspace(nat_char a)
52 {
53 return isspace((unsigned char) a);
54 }
55
56
57 static __inline nat_char
nat_toupper(nat_char a)58 nat_toupper(nat_char a)
59 {
60 return toupper((unsigned char) a);
61 }
62
63
64
65 static int
compare_right(nat_char const * a,nat_char const * b)66 compare_right(nat_char const *a, nat_char const *b)
67 {
68 int bias = 0;
69
70 /* The longest run of digits wins. That aside, the greatest
71 value wins, but we can't know that it will until we've scanned
72 both numbers to know that they have the same magnitude, so we
73 remember it in BIAS. */
74 for (;; a++, b++) {
75 if (!nat_isdigit(*a) && !nat_isdigit(*b))
76 return bias;
77 else if (!nat_isdigit(*a))
78 return -1;
79 else if (!nat_isdigit(*b))
80 return +1;
81 else if (*a < *b) {
82 if (!bias)
83 bias = -1;
84 } else if (*a > *b) {
85 if (!bias)
86 bias = +1;
87 } else if (!*a && !*b)
88 return bias;
89 }
90
91 return 0;
92 }
93
94
95 static int
compare_left(nat_char const * a,nat_char const * b)96 compare_left(nat_char const *a, nat_char const *b)
97 {
98 /* Compare two left-aligned numbers: the first to have a
99 different value wins. */
100 for (;; a++, b++) {
101 if (!nat_isdigit(*a) && !nat_isdigit(*b))
102 return 0;
103 else if (!nat_isdigit(*a))
104 return -1;
105 else if (!nat_isdigit(*b))
106 return +1;
107 else if (*a < *b)
108 return -1;
109 else if (*a > *b)
110 return +1;
111 }
112
113 return 0;
114 }
115
116
strnatcmp0(nat_char const * a,nat_char const * b,int fold_case)117 static int strnatcmp0(nat_char const *a, nat_char const *b, int fold_case)
118 {
119 int ai, bi;
120 nat_char ca, cb;
121 int fractional, result;
122
123 assert(a && b);
124 ai = bi = 0;
125 while (1) {
126 ca = a[ai]; cb = b[bi];
127
128 /* skip over leading spaces or zeros */
129 while (nat_isspace(ca))
130 ca = a[++ai];
131
132 while (nat_isspace(cb))
133 cb = b[++bi];
134
135 /* process run of digits */
136 if (nat_isdigit(ca) && nat_isdigit(cb)) {
137 fractional = (ca == '0' || cb == '0');
138
139 if (fractional) {
140 if ((result = compare_left(a+ai, b+bi)) != 0)
141 return result;
142 } else {
143 if ((result = compare_right(a+ai, b+bi)) != 0)
144 return result;
145 }
146 }
147
148 if (!ca && !cb) {
149 /* The strings compare the same. Perhaps the caller
150 will want to call strcmp to break the tie. */
151 return 0;
152 }
153
154 if (fold_case) {
155 ca = nat_toupper(ca);
156 cb = nat_toupper(cb);
157 }
158
159 if (ca < cb)
160 return -1;
161 else if (ca > cb)
162 return +1;
163
164 ++ai; ++bi;
165 }
166 }
167
168
169
strnatcmp(nat_char const * a,nat_char const * b)170 int strnatcmp(nat_char const *a, nat_char const *b) {
171 return strnatcmp0(a, b, 0);
172 }
173
174
175 /* Compare, recognizing numeric string and ignoring case. */
strnatcasecmp(nat_char const * a,nat_char const * b)176 int strnatcasecmp(nat_char const *a, nat_char const *b) {
177 return strnatcmp0(a, b, 1);
178 }
179